Realization of Fractional-Order Proportional Integral Controller for a Class of Higher Order System–A Comparative Study

In this work, a fractional order proportional integral (FOPI) controller has been realized in complex \(z\) domain for a class of higher order plant model. The entire design methodology encompasses three stages. In the first stage, the FOPI controller is tuned based on certain design specifications. The second stage involves rational approximation of fractional controller using Oustaloup method. In the third stage, the FOPI controller is discretized using Tustin approximation and Al-Alaoui approximation, respectively. Finally, a simulation study is performed through comparing the discretized open loop frequency responses resulted from the two approximation methods with respect to the ideal frequency response characteristic.